NTSB Reports

Long-Hidden NTSB Reports Contain Flight Data

In late 2001 and early 2002, the
National Transportation Safety Board (NTSB)
filed reports detailing information of the four
commandeered flights,
based on a combination of air traffic control recordings and,
in the case of United Flight 93, the plane's
flight data recorder.
However, these reports remained hidden from public view for years.
Even today, the entries in the NTSB database for the 9/11/2001 crashes state:

The terrorist attacks of September 11, 2001 are under the jurisdiction
of the Federal Bureau of Investigation. The Safety Board provided requested
technical assistance to the FBI, and this material generated by the NTSB
is under the control of the FBI. The Safety Board does not plan to issue
a report or open a public docket

Excerpts from Flight Path Studies

The published reports include flight path studies for all of the flights
except Flight 93.
Below are illustrations from the studies showing ground paths
and altitude profiles.
The studies determined location and altitude
using transponder data when available,
and radar returns thereafter.